In order to effect consumable electrode arc welding, it is necessary that an electric current corresponding to the thickness of the base material and a proper voltage corresponding to the electric current be set.
Examples of the method of setting these welding conditions include an individual method of individually setting electric current and voltage and a unitary method by which the welding machine automatically sets a proper standard voltage when an electric current is set.
FIG. 3 illustrates a welding device which gives welding command by an individual method and the reference numeral 111 indicates an input device and the reference numeral 112 indicates a control device which controls various units and has a main memory portion 112 and a welding condition command portion 114. The reference numeral 115 indicates a welding device machine. In order to set welding conditions in such a welding device, a predetermined value of welding current and a predetermined value of welding voltage are inputted from the input device 111, and these predetermined values are stored in the main memory portion 113 and then sent from the welding condition command portion 114 to the welding machine 115. Thus, as a command to the welding machine 115 there is used the value inputted as it is, making it necessary for the operator which sets conditions to input an electric current and a proper voltage corresponding to the electric current and hence have an expert knowledge of the relationship between welding current and voltage.
FIG. 4 illustrates a welding device which gives welding command by a unitary method and has a unitary voltage table portion 219 and a welding voltage judgment portion 216 in a welding machine 215. In this welding device, the operator who sets welding conditions sets only electric current value among welding conditions using an input device 211. This electric current value is stored in a main memory portion 213, and the condition which is ordered to the welding machine 215 by a welding condition command portion 214 is only electric current value. When ordered electric current, the welding machine 215 finds out the standard voltage corresponding to the electric current from a unitary voltage table portion 219 in itself and then outputs proper welding conditions composed of the electric current thus given and the voltage found out in the unitary voltage table portion 219. Thus, the unitary method requires that the operator who sets conditions order only electric current value and is advantageous in that no expert knowledge of the relationship between welding current and voltage is needed. As the relationship between welding current and voltage housed as a numerical value table in the unitary voltage table portion 219 there is normally used one prepared by welding machine manufacturers.
Further, as disclosed in Patent Reference 1, a welding electric supply is proposed which operates with a unitary voltage outputting portion of outputting a unitary voltage as a proper voltage command value corresponding to welding current, which unitary voltage outputting portion is provided in an arc welding device such as robot, whereby switching is made from individual method to unitary method or vice versa.
Patent Reference 1: U.S. Pat. No. 3,287,335 (corresponding to U.S. Pat. No. 6,384,375)